package burp;

public class Base64
{
  public static String byteArrayToBase64(byte[] a)
  {
    return byteArrayToBase64(a, false);
  }
  
  public static String byteArrayToAltBase64(byte[] a)
  {
    return byteArrayToBase64(a, true);
  }
  
  private static String byteArrayToBase64(byte[] a, boolean alternate)
  {
    int aLen = a.length;
    int numFullGroups = aLen / 3;
    int numBytesInPartialGroup = aLen - 3 * numFullGroups;
    int resultLen = 4 * ((aLen + 2) / 3);
    StringBuilder result = new StringBuilder(resultLen);
    char[] intToAlpha = alternate ? intToAltBase64 : intToBase64;
    

    int inCursor = 0;
    for (int i = 0; i < numFullGroups; i++)
    {
      int byte0 = a[(inCursor++)] & 0xFF;
      int byte1 = a[(inCursor++)] & 0xFF;
      int byte2 = a[(inCursor++)] & 0xFF;
      result.append(intToAlpha[(byte0 >> 2)]);
      result.append(intToAlpha[(byte0 << 4 & 0x3F | byte1 >> 4)]);
      result.append(intToAlpha[(byte1 << 2 & 0x3F | byte2 >> 6)]);
      result.append(intToAlpha[(byte2 & 0x3F)]);
    }
    if (numBytesInPartialGroup != 0)
    {
      int byte0 = a[(inCursor++)] & 0xFF;
      result.append(intToAlpha[(byte0 >> 2)]);
      if (numBytesInPartialGroup == 1)
      {
        result.append(intToAlpha[(byte0 << 4 & 0x3F)]);
        result.append("==");
      }
      else
      {
        int byte1 = a[(inCursor++)] & 0xFF;
        result.append(intToAlpha[(byte0 << 4 & 0x3F | byte1 >> 4)]);
        result.append(intToAlpha[(byte1 << 2 & 0x3F)]);
        result.append('=');
      }
    }
    return result.toString();
  }
  
  private static final char[] intToBase64 = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' };
  private static final char[] intToAltBase64 = { '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':', ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?' };
  
  public static byte[] base64ToByteArray(String s)
  {
    return base64ToByteArray(s, false);
  }
  
  public static byte[] altBase64ToByteArray(String s)
  {
    return base64ToByteArray(s, true);
  }
  
  private static byte[] base64ToByteArray(String s, boolean alternate)
  {
    byte[] alphaToInt = alternate ? altBase64ToInt : base64ToInt;
    int sLen = s.length();
    int numGroups = sLen / 4;
    if (4 * numGroups != sLen) {
      throw new IllegalArgumentException("String length must be a multiple of four.");
    }
    int missingBytesInLastGroup = 0;
    int numFullGroups = numGroups;
    if (sLen != 0)
    {
      if (s.charAt(sLen - 1) == '=')
      {
        missingBytesInLastGroup++;
        numFullGroups--;
      }
      if (s.charAt(sLen - 2) == '=') {
        missingBytesInLastGroup++;
      }
    }
    byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];
    

    int inCursor = 0;int outCursor = 0;
    for (int i = 0; i < numFullGroups; i++)
    {
      int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
      result[(outCursor++)] = ((byte)(ch0 << 2 | ch1 >> 4));
      result[(outCursor++)] = ((byte)(ch1 << 4 | ch2 >> 2));
      result[(outCursor++)] = ((byte)(ch2 << 6 | ch3));
    }
    if (missingBytesInLastGroup != 0)
    {
      int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
      int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
      result[(outCursor++)] = ((byte)(ch0 << 2 | ch1 >> 4));
      if (missingBytesInLastGroup == 1)
      {
        int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
        result[(outCursor++)] = ((byte)(ch1 << 4 | ch2 >> 2));
      }
    }
    return result;
  }
  
  private static int base64toInt(char c, byte[] alphaToInt)
  {
    int result = alphaToInt[c];
    if (result < 0) {
      throw new IllegalArgumentException("Illegal character " + c);
    }
    return result;
  }
  
  private static final byte[] base64ToInt = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
  private static final byte[] altBase64ToInt = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 };
}
